Constant-current series motor.



PATENTED AUG. 23, 1904.

M. LEBLANO. CONSTANT CURRENT SERIES MOTOR.

APPLICATION FILED FEB. 26, 1903.

N0 MODEL.

ffMQ MW.

UNITED STATES Patented August 23, 1904.

PATENT OEEIcE.

MAURICE LEBLANC, OF PARIS, FRANCE, ASSIGNOR TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

CONSTANT-CURRENT SERIES MOTOR.

SPECIFICATION forming part of Letters Patent No. 768,467, dated. August 23, 1904.

Application filed February 26, 1903. Serial No. 1%,282. N0 model.)

To all whom it nu/47 concern: I

Be it known that I, MAURICE LuBLANo,a citizen of the Republic of France, residing at i Villa Montmorency, No. 1 Avenue de Boufl fleurs, Paris, France,-have invented a new and useful Improvement in Regulators for Constant-Current Series Motors, of which the following is a specification.

The object of this invention relates to the regulation of a motor whose field has a series winding which is placed in a main line through which direct current of constant strength is at all times made to pass by properly regulating the generators in said main line in any well-known manner. Now it is well known that if we disregard armature reactions such a motor under such conditions has no definite speed for a given load. It is as likely to run fast and even to race as to run slow; but if we take into account armature reactions we find there is a certain permissible maximum load which the motor may carry. If greater load than this maximum load is placed upon the motor, it will not start. If the maximum load or a load very nearly equal to the max imum load is placed upon the motor, the moi tor will start and run at slow speed. If this j load be now diminished, the motor speeds up l until the hurtful electric reactions, the eddycurrents, and the mechanical friction of the l motor at the greater speed added to the di- 1 minished load on the motor produce a new l y l l l state of equilibrium at some higher speed. At a load considerably below the maximum the motor will run at a very high speed indeed, which means that it will race. Such automatic regulation of a series-wound motor supplied by a direct current of constant strength as has just been discussed is naturally very ineflicient.

It is the object of my invention to devise an l efiicient arrangement of electrical apparatus so as to vary the field of a series-wound motor fed with constant direct current with relation to its velocity, so that this velocity shall never exceed such an arbitrarily-fixed maximum as I may choose to select, no mat- 5 ter how small the load, and shall, in fact, be not far from constant. To this end I take a dynamo and arrange it to revolve at a speed which shall be uniform with relation to the speed of the motor. Thus I may mount the dynamo upon the shaft of the motor so as to insure that when the motorruns slowly the dynamo shall run slowly and when the motor runs fast the dynamo shall run correspondingly fast. I thereupon so design thisdynamo and electrically connect it to the motor in such a manner that'at slow speeds of the motor, and therefore slow speeds of the dynamo, the dynamo shall furnish practically no current to the motor-field opposing the effect of its series winding; but as the motor reaches its selected maximum speed,no matterwhether the load be great or small, the now more rapidly revolving dynamo shall quite suddenly furnish sufficient opposing current to the motor-field to practically neutralize the motor-field. In this way it is seen that the speed of the motor can never exceed the selected maximum, for when the motor reaches this maximum speed the dynamo, which now revolves rapidly, suddenly generates an opposing current sufiicient to practically wipe out the motor-field, which means that the 1 motor must slow down.

The dynamo shouldbe self-exciting. Its design will be such that the magnetization of its field will not build up to any appreciable extent at slow speeds, but that it will build up quite rapidly at a speed corresponding to the preselected maximum speed of the motor. Furthermore, it is desirable that the field of this dynamo should have very little residual magnetism and that its armature-circuit be closed in derivation upon the series winding of the motor-field, so that the field of the dynamo may always have an initial excitation, which is, however, very small, from which its field can be built up when the proper velocity has been reached Without relying upon any residual magnetism in the dynamo.

In the drawings, Figure 1 shows a diagram of a main circuit containing motors and reglating dynamos connected therewith, and the series winding B of the motor, and thereing to neutralize the magnetizing effect of i I further design my regulator-dynamo so Fig. 2 shows the characteristics of the regufore to practically wipe out the magnetic field 6 lating-dynamo. l of the motor. It follows at once that the mo- The main dynamo K, which is indicated tor, no matter whether its load be great or 5 conventionally, feeds a main circuit XY with l small, can never attain a greater speed than a direct current of constant strength. In this I such as corresponds to that speed of the dymain circuit are placed one or more direct- 1 namo at which its field excitation has built up 70 current motors A, having commutators A sufiiciently for it to produce such a current in and brushes A, which brushes are in series the opposed winding C of the motor as will to with the field-winding B of the motor. neutralize the field of the motor. It equally Mounted upon the motor-shaft or arranged follows that a comparatively small diminuwith respect to the motor in any other suittion of the velocity of the motor, and there- 75 able way to produce a constant relative speed fore of the dynamo,below this maximum speed is a small dynamo C, whichis wound to be will, if its residual magnetism is negligible,

I5 self-exciting. I have indicated a series-wound bring about the withdrawal of the building-up dynamo, the series field-coil E of which is action in the dynamo-field, so that the dynamo mounted in series with the brushes D which will no longer send an appreciable current into 80 bear upon the commutator D of the dynamo the opposed winding C of the motor.

D. The armature-circuit of this dynamo D I have already remarked that it is desirable supplies a winding C, which is mounted upon to reduce the residual magnetism of the reguthe field of the motor A in opposition to its lating-dynamo to the lowest possible point. field-winding B. This opposed winding C, I I may further remark that it is desirable to 85 usually make of high resistancethat is, of thoroughly laminate the fields of the motor fine wireand I further prefer to mount the and of the regulating-dynamo to render their external circuit of the dynamo D, which conmagnetic circuits very permeable in reducing tains the opposed winding C, in derivation of the air-space to a minimum and not to satuthe field-windingB of the motor or in derivarate the iron. 9 tion of a part of this winding. In this man- I come now to an explanation of the charner I secure the presence of a small excitingacteristic curve of the regulator-dynamo with current in the field-winding E of the dynamo relation to the. problem in hand. Referring D without having to rely on any residual to Fig-2, I have shown a set of rectangular magnetism in the dynamo, which residual coordinates, thehorizontal axis Ot'being taken 95 magnetism it is of advantage to make as to measure the current strength, and the vernearly equal to zero as possible. I also artical axis 01; being taken to represent elecrange the connections so that the current trical pressure. It is well known that if a which initially passes through the coil 0 as a series-wound dynamo is run at a certain conbranch of the main-line current is opposed stant speed. IN the curve which represents the 0 in magnetic effect to the currentin the coil B. relation between current strength and elec- Nevertheless the current which traverses the trical pressure under varying resistances in the 4 opposed winding C will be small atlow speeds current is of the general shape represented at of the motor, and therefore of the dynamo, so OMVV. I have drawn the straight line OR that at such speeds the counter magnetizing such that the tangent of the angle ROz' shall I05 force due to the opposed winding C will be be equal to, the total resistance in the armanegligible with respect to the magnetizing ture-circuit of my regulator-dynamo. Under force of the series winding B of the motor. such assumptions it is explained in the text- The strength of the field of the motor at slow books that when the regulator-dynamo is runspeeds will thus not be sensibly diminished ning at a speed WV to supply a circuit of total IIO by the presence of the dynamo D and the opresistance R the regulator-dynamo will give posed winding C. of? a current proportional to the length 01 5 As the motor and inconsequence the dyunder an electrical pressure proportional to namo increase in speed the strength of the the length IM. My regulator-dynamo must current in the winding 0 will increase; but it therefore be designed so that the length OI II 5 will increase very slowly at first and then very corresponds to the strength of current necessuddenly, when the velocity of the dynamo sary to send into the opposed winding C of 5 5 has become sufiicient to permit it to build up the motor Ato nearly or completely neutralits excitation. The dynamo is so designed ize the field of the motor or the effect of its that this last-mentioned velocity shall correseries winding B at what now becomes a pre- I2 spond to the maximum velocity which'it is deselected maximum speed W, being the speed sired that the motor shall have irrespective of which the motor is never to exceed whether 6 the size of the load and that the current genwith a small or a large load. I speak of erated by the dynamo at this velocity shall be this speed as the common maximum speed sufiicient when traversing the opposed windpredetermined alike for all loads. If now 5 that the portion of its characteristic curve OM for the maximum speed V very nearly coincides with the straight line OR, it will be found that the characteristic of the dynamo for a speed W but little less than the maximum speed V will fall almost entirely below the straight line OR and will intersect this straight line in a point P very near the origin of coordinates. This means that at the arbitrarily-selected speed W, somewhat less than the maximum permitted speed the amount of current which the dynamo under the given assumption sends into the opposed winding C of the motor will be proportional to the the length OJ -*that is to say, it will be very small. Knowing the amount of this opposing current, we can readily deduce therefrom the intensity of the motor'field and in consequence the value K of the couple developed upon its axis when it turns with the velocity WV. This couple K will be somewhat though but little less than the theoretical maximum couple K, which the motor has at starting or zero speed.

So long as we do not put a greater load upon the motor than corresponds to the couple K the speed of the motor will not sink below the speed WV. Since this speed need be taken but little below the selected maximum speed W, as the characteristic curves on Fig. 2 show, it follows that so long as our motor is not required to overcome a resisting couple greater than K, which is but little less than the theoretical maximum couple K which the motor can stand, the speed of my motor will vary only between the limits TV and W, and these may be taken quite near together. as Fig. 2 shows. This means that my motor operates under practically constant speed from zero load up to that represented by the couple K.

While I have spoken of completely neutralizing the motor-field at the maximum permitted velocity, it will be understood that in actual practice it may not ordinarily be necessary to completely neutralize this field.

1. A line carrying a direct current of constant strength, a motor in the line having a field-winding in series with its armature, and a dynamo arranged to revolve at a uniform relative speed with the motor and to supply it with a current which practically neutralizes the motor-field at a certain common maximum velocity predetermined alike for all loads, substantially as described.

2. A line carrying a direct current of constant strength, a motor in the line having a field-winding in series with itsarmature, and a dynamo of low residual magnetization arranged to revolve at a uniform relative speed with the motor and to supply it with a current which practically neutralizes the motorfield when the motor has reached a common maximum velocity predetermined alike for all loads, substantially as described.

3. A line carrying a direct current of constant strength, a motor on the line having a field-winding in series with its armature, and a self-exciting dynamo of low residual magnetization arranged to revolve at a uniform relative speed with the motor and to supply it with a current which practically neutralizes the motor field when the motor has reached a common maximum speed predetermined alike for all loads, substantially as described.

et. A line carrying a direct current of constant strength, a motor in the line having a field-winding in series with its armature, and a dynamo arranged to revolve at a uniform relative speed with the motor and to supply the motor field with current opposed in effect to that of its series winding. said dynamo having the circuit which it supplies mounted in derivation of the series field of the motor, substantially as described.

5. A line carrying a direct current of constant strength, a motor in the line having a field-winding in series with its armature, and a dynamo of low residual magnetization arranged to revolve at a uniform relative speed with the motor and supplying a high-resistance winding on the motor-field with current opposed in efiect to that of its series winding, said dynamo having the high-resistance winding which it supplies mounted in derivation of the series field-winding of the motor, substantially as described.

6. A line carrying a direct current of constant strength, a motor in the line having a field-winding in series with its armature and a field-winding opposed thereto, and a dynamo arranged to revolve at a uniform relative speed with the motor, which dynamo supplies the opposed field-winding of the motor, the dynamo being so proportioned that its characteristic curve, at the speed corresponding to the maximum speed of the motor for all loads, practically coincides, on the sides toward the origin, with the straight line representing the resistance of the dynamo-circuit, substantially as described.

7. A line carrying a direct current of constant strength, a motor in the line having a field-winding in series with its armature and a dynamo, having a series field-winding, arranged to revolve at a uniform relative speed with the motor and designed so as to suddenly build up its field magnetization, when a speed corresponding to the maximum desired speed of the motor for any and all loads is reached, to then supply to the motor-field a current which practically neutralizes it, substantially as described.

8. The combination with a constant directcurrent-supply circuit, of a series-wound mo- & 768,467

tor in said circuit, in regulating dynamo of In testimony whereofIhave signed my name 10W residual magnetization driven by the to this specification in theprescnce of two submotor and primed by a portion of the linescribing Witnesses. current, and clernzignetizing-coils of high resistance upon the motor field-magnet and in 1 lVitnesses: the regulating-dynamo circuit, substantially l ARMAND LEBLANO,

as described. 1 AUGUSTUS E. INGRAM.

MAURICE LEBLANC. 

